Starboard 240V power cord

[keywasted]

As a 48 CPMY newbie owner there is much that I am discovering. First out of the bag is the Starboard Cable master 240 VAC hookup that only has a 3 wire cord. What gives? The port side has a standard 4 wire cord. Did Hatteras do something that I missed in electrial 101? Can anybody clue me in as my electrician can't? It won't transfer power on the panela and the panel breaker appears to be a 2 sided power source as well.

[Hatt36]

If your boat has an isolation transformer, only three wires are needed. However, I have no explanation for the difference is performance between the sides.
Richard

[DaveP]

It sounds like someone at some point opted to save some money and install a 3 wire 120 50amp cord on one side. The only difference between the 120 and the 240 is one wire. That is for the second leg of 120 input and the reason your stbd side shore power will not provide the proper power to your main board. Essentially you are only getting one of the needed two legs of 120 volt power in order to get your 240 volt service up. You should be still able to run all your 120 volt items you just won't have 240 service until you install a 4 wire 240 shore cord.

The only other way to correct this is to install a transformer at the junction of the 120 50amp supply to step up your 120 service to 240. But doing this will drop your available amperage to 25 from 50 I believe. But you'll have 240 service without having to replace your shore cord.

[captcoop]

I have a 45C that has a 240V and a 120V system. In the electrical panel there is a switch to select between the two. It is a nice feature for me when I take the boat to my dock at home as I only have one 30 amp outlet. This will run the essential needs.

[dshuman]

Likely somebody made an undocumented change, which can be tricky or dangerous. Stop now and track the wires down and check them with a test meter so you KNOW before you GO. You need to make sure the ground is isolated correctly to prevent electrolysis from eating away metal parts in contact with the water, and you sure don't want to connect hot to neutral directly. 240v input needs 4 wires for hot, hot, neutral and ground. The two hot wires are out of phase with each other so it's like two 120v inputs with a common neutral and a common ground.
I'm unfamiliar with the 48CPMY, but on my 53MY there are both 120v and 240v sockets on both sides of the boat. Does your boat have other regular input sockets for 120 and 240? Are there 2 separate 120v systems like the 53MY?

[Genesis]

At least my 45C does, and so do most of the others I've seen.

With them, you DO NOT need neutral connected. Indeed, it goes nowhere on the transformer!

If someone botched/butchered the socket they installed, however, STOP RIGHT NOW and fix that. Someone will get killed or you will destroy things on board some day with an improper socket on board for a shore cord. You may know what's what, but someone else will not.

The 250V/50A socket is standardized an has three pins and the "case" of the plug (around the circumference) is ground. The 120V/30A socket has three pins and NO case on the plug.

Check it out and see what you really have.... miswired AC inlets are extremely dangerous and can either kill people, cause fires or result in HUGE electrolysis problems and damage.

[keywasted]

I do have a four wire power cord in the Aft portside cablemaster???? Then on the port side mid-ship is a standard 240V out let. The starboard side also has a 30 amp outlet. The starboard cablemaster cord leads to a box in the engine room that is only a 3 wire box. Black, white and ground. It is a bloody puzzle and nothing on the starboard side is going to get plugged in until I get it figured out. Any 48 CPMY of '94 vintage out there?

[DaveP]

I think you have a 120 volt 50 amp cordset. It is a three wire with case and looks indetical and will plug into a 240/50 inlet. But it WILL NOT give you 240! The 120/50amp cordset has only ONE hot wire, a ground, and a negative.
What may have happened is somewhere the previous owner encountered a marina or dock with only 120 service and wanted to draw 50 amps instead of 30 amps so he installed a 120 50amp cordest.
I think if you have only three wires coming into the boat from the power inlet that as long as two are hot and one is the negative, then you have as Genesis suggested and have a transformer in line. If you have one hot, one negative and one ground then you do not have a transformer and you need to rewire the inlet to accept 240 volts. All you'd have to do is install another 4 wire 240/50amp cordset in place of the three wire cordset, and a matching 240 volt female power inlet in the boat. You can wire it the same as your 240 volt side is.
It's easy to test to find out what you have with a meter. Unplug the shortie from the boat, plug into 240/50amp shorepower and connect a meter. Connect the ground to the case and and the hot lead to each wire in turn and see if you have two 120 legs. If you do then you have 240 volts to that inlet. Then you need to make sure that your inlet is proper and you have a transformer in line. If you don't then you need to rewire if you want 240 from both sides.